You want to know about Dana Hunter, then, do you? I'm a science blogger, SF writer, compleat geology addict, Gnu Atheist, and owner of a - excuse me, owned by a homicidal felid. I loves me some Doctor Who and Roger Clyne and the Peacemakers. Sums me up. I'm a Midwest-born Southwesterner transplanted to the Pacific Northwest, which should explain some personality quirks, the tendency to sprinkle Spanish around, and why I'll subject you to some real jawbreakers in the place names department. My cobloggers, Karen Locke, Jacob and Steamforged, and I are delighted to be your cantineras y cantinero. Join us for una tequila. And feel free to follow @dhunterauthor on Twitter. Salud!

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Most of us know the basics of uniformitarianism: processes we see acting today acted in the past, and explain what we see in the geologic record. It includes the concept of gradual change over time (which is one of those things that got Darwin thinking along the path that led him to evolution). But Dr. Scott makes an excellent point that states more clearly than any other source I’ve heard why Flood geologists and other creationists are so very wrong when they point to events like the eruption of Mount St. Helens and the spectacular erosion seen in its aftermath, and claim this as proof that the Earth’s geology was created in catastrophe instead of forming gradually over time:

“Uniformitarianism, by the way, does not mean that everything that happened in geological history is slow and gradual. Lyell and Darwin and the other scientists of the day knew that there were catastrophic events that produced geological changes, but it’s the process that is the uniformity, as it were, from one time to another. The rate doesn’t have to be the same.”

Keep that quote handy. If you spend much time round Mount St. Helens, you’ll eventually run into flocks of creationists who love to misunderstand uniformitarianism. Their misunderstanding may be willful – but they’ll have a much harder time confusing innocent bystanders if you explain catastrophes (though not worldwide floods) are very much a part of genuine geology.

As I understand it, from Lyell’s time until roughly the mid 20th cy., geologists were unwilling to accept the occurrence of any catastrophes much larger than well-documented ones, like floods much larger than any that were well-documented. J Harlen Bretz’s hypothesis of the Columbia River giant floods was rejected for some decades before it became accepted. A certain crater in Arizona had a lot of controversy over how it was formed. An impact? A volcano?

I think that a reason was that giant catastrophes seemed too much like hand waving, too much like that famous cartoon that features “and then a miracle occurs”, too poorly defined.

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But over the mid to late 20th cy., geologists succeeded in making some giant-catastrophe hypotheses testable.

About the Columbia River giant floods, their water source was located: a former lake near Missoula, MT. The flow features along the Columbia River resemble those in various rivers, but much larger.

That Arizona crater was identified as an impact crater from the shock metamorphism of some of its rocks, as if those rocks had been hit by some super hammer. Shock metamorphism has been discovered at various other places, and there are nearly 200 impact craters now recognized on our planet. However, many of them are heavily eroded and difficult to recognize.

More recently, geologists have discovered evidence of catastrophes associated with some mass extinctions, like the K-T and P-Tr ones.

The nowadays favorite hypothesis of the origin of the Moon involves a big collision early in the Solar System’s history, a collision that spewed lots of fragments that went into orbit and condensed into the Moon.

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This revival of catastrophism was not the result of armchair philosophical debates but a result of testing hypotheses about specific possible catastrophes. It wasn’t the result of armchair pontificating and philosophizing.